Automatic density regulator



United States Patent O i AUTOMATIC DENSITY REGULATOR Cass B. Levi, Pittsburg, Kans., assignor to The McNally- Pittsburg Manufacturing Corporation, Pittsburg, Kans., a corporation of Kansas Application March 8, 1954, Serial No. 414,789

7 Claims. (Cl. 209-1725) The invention relates to the art of gravity separation of solid materials by means of an aqueous suspension of tine solid particles and has reference more particularly to the provision of improved apparatus for automatically maintaining the aqueous suspension at the particular density desired.

The separation of solid materials having ditferent specific gravities by means of an aqueous suspension of line solid particles has been employed in the cleaning of coal by separating the coal which oats in the suspension bath from the accompanying impurities which sink to the bottom of the bath. The invention is especially applicable to a system wherein the suspension bath is maintained at a speciiic gravity which is greater than the float solids but less than that of the sink solids, and wherein the bath media comprises finely divided solids such as magnetite and water.

The coal or other product to be separated is fed to the bath in which the light solids iioat to the top with the heavy solids sinking to the bottom, and the iioat and sink solids thus separated are removed from the bath together with some of the bath medium which adheres thereto. Most of the adhering medium 'is drained from the solids on drainage screens and the same is delivered to a heavy medium circulating sump from which the medium is returned to the bath circuit. The medium remaining on the solids is rinsed therefrom on rinsing screens and this dilute medium is thickened by gravity settling methods to recover the medium, which is thereupon also delivered to the heavy medium circulating sump.

An obj-ect of the invention is to provide an improved density regulator which will automatically control the density of the recovered medium delivered to the bath circuit.

Another and more specific object of the invention resides in the provision of a density regulator for a dense media separation system which will continuously sample the recovered medium by means of a testing hydrometer and wherein movement of said hydrometer is employed to return the recovered medium to the bath circuit if it is of the required density.

Another object of the invention is to provide a density regulator of the character described wherein the testing hydrometer is suspended by a balance beam which is not required to do any work other than overcome the negligible friction of its pivot bearings when the balance beam is moved by movement of the hydrometer as dictated by the density of the medium, and wherein all mechanical connections between the balance beam and the mechanism actuated thereby have been eliminated.

A further object is to provide a regulator for controlling thedensity of the recovered medium in a dense media system wherein the mechanical connections above referred to are replaced by electrical means in the form of inductance coils included in the armature circuit of a positioning motor, and wherein movement of the balance beam varies the impedance of the respective coils to 2,717,078 Patented Sept. 6, 1955 "ice infinitely vary the position of the armature within its angular range.

With these and various other objects in View, the invention may consist of certain novel features of construction and operation, as will be more fully described and particularly pointed out in the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the device and wherein like reference characters are used to designate like parts- Figure l is a schematic View illustrating a iiow Sheet of a density regulator coming within the invention and wherein arrows indicate theflow of the liquid in the various pipes and vessels; and

Figure 2 is a sectional View of the knife edge connection for the hydrometer, taken substantially along line 2 2 of Figure 1.

Referring to the drawings and particularly Figure 1, the pipe 10 has connection with the dilutek medium circuit of a dense media separation system and functions to continuously divert some of the dilute medium to the recoveryV cone indicated by the numeral 11. The said recovery cone has an overflow launder 12 connecting with the discharge pipe 13 which removes from the system the tine slimes overiiowing the recovery cone. It will be understood that the dilute medium in the recovery cone is allowed to settle and to thicken to the desired density for return to the bath circuit. The' outlet pipe 14 connects with the apex of the recovery cone at the bottom thereof and said pipe has associated therewith the air lift 15, which functions to assist in the withdrawal of the medium from the cone and the deliveryof the same upwardly through pipe 16, which is divided at 17, thereby providing two paths of ow for the medium, one

path comprising the pipe 18 and the other lthe pipe 20.

Pipe 18 functions to deliver a quantity of the medium to the testing vessel 21, whereas pipe 20fdelivers to the regulator 22, consistingyof a diverting Vgate enclosure provided with the diverting gate 23. With the diverting gate in the position as shown, it willbe understood that the medium delivered to the regulator by the pipe 20 will be diverted to the left hand side and caused to tlow into pipe 24 which `returns the medium to the bath circuit. Should the diverting gate 23 be located in the dotted line position it will be understood that the medium delivered to the regulator will be diverted to the right hand side and `will accordingly be delivered to pipe 25 so that the medium thus diverted is returned to the recovery cone for further thickening.

The testing vessel 21 is substantially cylindrical in shape, having an open top and into which is directed the downturned end, that is, the delivery end of the pipe 18. Adjacent the top end of the testing vessel there is provided an overflow pipe 31. The bottom" of the testing Vessel is provided with an outlet orice positioned directly above a funnel-shaped receiver 26 having connection at 32 with pipes 31 and 27 so that the medium flowing through the'testing vessel and that overflowing the same is all returned to the diverting gate for distributon as directed by the regulator. i erated in a manner to continuously supply a small quantity of bath medium to the testing vesselV to maintain submerged the streamlined hydrometer bulb 33. YThe outlet orifice 30 presents an' orifice of fixed size through which the medium leaves -the testing vessel,i thus preventing thickening of the medium in the vessel and at the same time continuously presenting new medium for testing. The overow maintains the medium in the vessel at a constant level.

The hydrometer bulb 33 is suspended by the rod 34 having a knifel edge connection as at 35, see Figure 2, with one end of a balance beam 36. At an intermediate The air lift is oppoint the balance beam is pivotally supported by means of a pair of precision ball bearings 37 suitably supported by the standards 38. The beam is counterbalanced on that side of the pivot opposite the hydrometer bulb by the adjustable member 40 which may be located in various adjusted positions along the beam in order to select the particular specific gravity as desired for the recovered medium. Thus, for any given setting, the vertical position of the hydrometer bulb responds to the density of the medium in the testing vessel. A secondary adjustment on the balance beam may be provided in order to compensate for the effects of the vertical flow past the surface of the bulb.

In accordance with the invention a soft iron core 41 is fixed to the left end of the balance beam 36, being interposed vertically at right angles to the beam. The respective ends of the soft iron core 41 are positioned within hollow cylindrical coils 42 and 43, one being located above the beam and the other below the beam so that as the hydrometer may eiect pivotal movement of the beam,

due to a deviation in the density of the medium, either above or below the desired density, the iron core 41 is caused to enter one coil and leave the other. The coils 42 and 43 are electrically connected by means of conductors 44, 45 and 46 to a positioning motor indicated in its entirety by numeral 47. Movement of the iron core Within the induction coils will change the impedance, or apparent resistance of said coils, increasing one and decreasing the other. The said conductors connect with a variable resistance in the positioning motor in such manner, that as the impedance of the coils is changed, the motor armature is rotated until both sides of the variable resistance in the motor balances the changed resistance in the two coils. The armature of the positioning motor 47 is thus rotated and it will be understood that the position of said armature is innitely variable within its angular range.

A positioning motor such as disclosed and claimed in the Edmondson Patent 2,127,680 of August 23, 1938, has been found completely satisfactory for the purposes of the present invention. The motor is electrically connected to a suitable source of electrical energy by means of conductors L1 and L2, and the armature shaft 48 has the crank arm 50 xed thereto on the right hand side of the motor, with the cam 51 being xed to the armature shaft at the left hand end. The crank 50 is suitably connected by link 52 with the plunger of an air valve 53, which is supplied with air under pressure from the air supply pipe 54 and which functions in a manner to regulate the supply of compressed air through pipe S to the air lift 15. The armature of the motor 47 accordingly positions the crank arm 50, and said arm actuates the air valve 53 to control the compressed air supplied to the air lift. Depending on the density of the recovered medium as determined by the testing hydrometer, the plunger of the air valve 53 will move in and out to vary the effective action of said air lift.

The microswitch 56 is positioned for actuation by cam 51. One terminal of the switch is electrically connected by conductor 57 to conductor L1 of the power supply. The other terminal of the microswitch is electrically connected by conductor 58 to an air valve, indicated generally by numeral 60, of the electromagnetic type, with the control member of the valve being biased toward end 61 when the electromagnet of the valve is deenergized, and being magnetically moved into end 62 when the magnet is energized. Conductor 63 completes the electrical connection to the electromagnetic air valve, the same having connection with conductor L2 at 64.

The end 61 of the electromagnetic valve 60 has connection through pipe 65 with the left end of the doubleactng air cylinder 66. In a similar manner end 62 of the electromagnet has connection through pipe 67 with the right hand end of the double-acting air cylinder 66. The piston 68' is adapated to reciprocate Within the air cylinder and the piston rod 70 connects the piston with the diverting gate 23. When the electromagnetic valve is deenergized, compressed air from the supply pipe 54 is directed into pipe 65 and supplied to the left hand end ot' the air cylinder. Thus, the piston 68 is forced to the right and the diverting gate 23 is located as shown in Figure 1, in which position of the gate the bath medium delivered to the regulator is diverted to pipe 24 which returns the medium to the bath circuit. When the electromagnetic valve is energized, compressed air from supply pipe 54 is delivered to pipe 67 which will elect movement of the piston 68 in a direction toward the left. As a result the diverting gate will be located to the left in its dotted line position, as shown in Figure l, in which position of the gate the bath medium entering the regulator will be delivered to pipe 25 and returned by said pipe to the recovery cone for further thickening.

En the automatic density regulator of the invention all mechanical connections have been eliminated between the balance beam 36 and the mechanism actuated thereby including the air valve 53 and the diverting gate 23. Therefore the beam is not required to do work other than to overcome the negligible friction of its pivot bearings in order to position itself as dictated by the density of the medium. As long as the recovered bath medium remains at the desired density the hydrometer 33 will assume a neutral position and no corrective action will take place since the iron core 41 will extend an equal distance into both inductance coils 42 and 43, and since the impedance or apparent resistance of said coils remains substantially balanced, the armature shaft 48 of the positioning motor also assumes a neutral position, as shown in Figure 1. The neutral position of the armature shaft of positioning motor 47 withdraws the plunger of the air valve 53 to an extent where the air lift is operative for continuously withdrawing some of the thickened medium from the recovery cone and discharging the same upwardly through pipe 16. Divided portions, respectively, of this withdrawn medium are continuously supplied to the regulator 22 and to the testing vessel 21. The quantity delivered to the regulator is diverted to pipe 24 and returns to the bath circuit since the same is of the desired density. The diverting gate is maintained in its right hand position since the electromagnetic valve 60 is deenergized due to the fact that the contacts of the microswitch 56 are open when the armature shaft 48 of the positioning motor is in a neutral position.

Should the density of the bath medium increase the hydrometer bulb 33 will call for a dilution of said medium by oating higher in the testing vessel. The inductance coils 42 and 43 thus become unbalanced and this in turn effects clockwise rotation of the armature shaft 48 of the positioning motor such as to withdraw the plunger from air valve 53, admitting more air to the air lift so that its F action increases the rate of withdrawal of the medium from the recovery cone. This necessarily results in a corresponding increase in the water to solids ratio, thus eifecting the required dilution.

In the event the density of the bath medium should fall below the predetermined setting, the hydrometer will sink in the testing vessel and this movement of the balance beam will also unbalance the impedance of the nductance coils 42, 43 but in this ease the unbalance is such as to rotate the armature shaft 48 counterclockwise. The

'- plunger is moved inwardly of the air Valve 53 to decrease the air supply to the air lift and should armature shaft 48 continue to rotate in a clockwise direction rotation of cam 51 will eventually close the contacts of the microswitch 56. The electromagnetic valve 60 will become energized and compressed air will be supplied through pipe 67 to the right hand end of the air cylinder 66 to thus locate the diverting gate 23 in its left hand position. The result of this positioning of the diverting gate 23 is to divert the bath medium delivered to the regulator to pipe 25, which returns it to the recovery cone for further thickening. As long asv the hydrometer bulb remains in a low position in the testing vessel a decreased quantity of air will be supplied to the air lift andthe diverting gate will continue to return the medium to the recovery cone. Eventually, however, the medium will increase in density due to continued delivery of medium solids to the recovery cone from the dilute medium circuit, whereupon the hydrometer bulb will rise to a neutral position andthe parts will be actuated to return them' to their neutral position as shown in Figure l.

The continuous testing and correction of the recovered medium results in extremely precise control in the density ofsuch medium and very ilttle diversion above or below the correct density is possible during operation of the system. During said operation, however,y it may be desirable to change the selected density of the recovered medium and this is accomplished merely by changing the setting of the member 40 on the balance beam.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated in the drawings, as various other forms of the device will of course be apparent to those skilled in the art without departing from the spirit of the invention or the scope ofthe claims.

What is claimed is:

l. In apparatus for automatically regulating the density of a liquid suspension comprising ultra-fine solids in water, the combination including a testing vessel, a balance beam, an hydrometer suspended from one end of the balance beam and having location in the testing vessel, inductance coils associated with the other end of the balance beam in a manner whereby the impedance of the coils is balanced only when the beam is disposed in a horizontal neutral position, means continuously delivering a quantity of said liquid suspension to the testing vessel to submerge the hydrometer therein and effect movement of the balance beam as the density of the liquid suspension may vary, and other means responsive to the balanced and unbalanced conditions of said inductance coils for diverting the liquid suspension delivered thereto to a bath circuit when the same has the correct density or a higher density, and for diverting the liquid suspension to a return circuit for thickening when the density of the same is below the correct density.

2. In apparatus for automatically regulating the density of a liquid suspension comprising ultra-tine solids in water, the combination including a testing vessel, a balance beam, an hydrometer suspended from one end of the balance beam and having location in the testing vessel, a pair of inductance coils associated with the other end of the balance beam in a manner whereby the impedance of the coils is balanced only when the beam is disposed in a horizontal neutral position, a regulator provided with a diverting gate, means continuously supplying a quantity of the liquid suspension to the regulator, and said means also supplying a quantity of said liquid suspension to the testing vessel to submerge the hydrometer therein and eect movement of the balance beam as the density of the liquid suspension may vary, and mechanism responsive to the balanced and unbalanced conditions of said inductance coils for actuating said diverting gate, whereby the liquid suspension supplied to the regulator is delivered to a bath circuit when the same has the correct density or a higher density, and is delivered to a return circuit for thickening when the density of the same is below the correct density.

3. In apparatus for automatically regulating the density of a liquid suspension comprising ultra-fine solids in water, the combination including a testing vessel having a fixed outlet orice and an overflow, a balance beam, an hydrometer suspended from one end of the balance beam and having location in the testing vessel, means supplying said liquid suspension to the testing vessel to submerge the hydrometer and effect movement of the balance beam as the density of the liquid suspension may vary, a pair of inductance coils associated with the other lend of the balance beam inl a manner causing a balanced condition as regards the impedance ofthe coils whenthe beam is disposed in a horizontal neutral positionV and an unbalanced condition when the beam is above or below said horizontal neutral position, a regulator provided with a diverting gate, an air lift for delivering a quantity of the liquid suspension to the regulator in a manner whereby the liquid to solids ratio of the suspension is increased inv proportion to the quantity of air supplied to the air lift, and mechanism responsive to the balanced and unbalanced conditions of said inductance coils-for actuating said diverting gate and for regulating the quantity of air supplied to the air lift, said diverting gatein'` one position delivering the liquid suspensionsupplied to the regulator to a bath circuit and in another position diverting the liquid suspension to a return circuit for further thickening.

4. In apparatus for regulating the density of a bath medium, the combination with a dilute medium circuit, a bath circuit, and a recovery cone, and wherein the medium from the dilute medium circuit is delivered to the recovery cone for thickening of a regulator having a positionable diverting gate, an air lift associated with the recovery cone and operative for withdrawing medium therefrom and delivering a portion of the same to the regulator, a testing vessel to which the remainder of the recovered medium is delivered for testing, a balance beam, an hydrometer suspended from one end of the balance beam and having location in the testing vessel, a pair of inductance coils associated with the other end of the balance beam in a manner whereby the impedance of the coils is balanced only when the beam is disposed in a horizontal neutral position, electric means responsive to the balanced and unbalanced conditions of said inductance coils for regulating the supply of air to said air lift and for actuating said positionable diverting gate, said diverting gate in one position returning the medium from the regulator to the recovery cone for further thickening, and said diverting gate in another position delivering the recovered medium to the bath circuit.

5. Apparatus for regulating the density of a bath medium as defined by claim 4, wherein the recovered medium is delivered to the testing vessel by the air lift, and wherein the electric means comprises an electric positioning motor.

6. In apparatus for regulating the density of a bath medium, the combination of a recovery cone for thickening the dilute medium delivered thereto, a regulator having a positionable diverting gate, a testing vessel, a balance beam, an hydrometer suspended from one end of the balance beam and having location in the testing vessel, an air lift associated with the recovery cone and operative for withdrawing the thickened medium therefrom at a rate governed by the quantity of air supplied to the air lift, said air lift delivering some of the thickened medium to the regulator and the remainder to the testing vessel, whereby the hydrometer is submerged in the medium and effects movement of the balance beam as the density of the medium may vary, means including a positioning motor for regulating the supply of air to the air lift and for also actuating the positionable diverting gate, electric means associated with the balance beam and connecting with the positioning motor and operative to eiect movement of the positioning motor in the same direction and proportional to movement of the balance beam, and said diverting gate in one position discharging the bath medium from the regulator to a bath circuit and in a second position discharging the bath medium from the regulator to a return circuit for return to the recovery cone.

7. `In an automatic density regulator for controlling the density of a recovered medium, in combination, a settling cone to which dilute medium is delivered for thickening by gravity settling to produce said recovered medium, a regulator having a positionable diverting gate,

said gate in one position discharging recovered medium to a bath circuit and in its second position effecting return of the recovered medium to the settling cone, testing means including an hydrometer and which is continu-` ously submerged in the medium to be tested and which has vertical movement as the density thereof may vary, an air lift associated with the settling cone and operative for withdrawing the recovered medium from the cone, said air lift operating at a variable withdrawal rate in proportion to the quantity of air supplied thereto, whereby the liquid to solids ratio of the recovered medium may be varied to regulate the density of the said medium, conduit means connecting the air lift with the regulator and with the testing means so that some of the recovered medium is delivered to the regulator and the remainder is delivered tothe testing means, and electric means responsive to movement of the hydrometer for regulating the supply of air to the air lift and for actuating the diverting gate, said electric means locating the divertinggate in position to discharge the recovered medium to the bath circuit when the density thereof is correct or higher, and said means locating the diverting gate to return the recovered medium to the settling cone when the density is below the correct density.

References Cited in the iile of this patent `UNITED STATES PATENTS 2,320,519 Hirst June 1, 1943 

1. IN APPARATUS OF AUTOMATICALLY REGULATING THE DENSITY OF A LIQUID SUSPENSION COMPRISING ULTRA-FINE SOLIDS IN WATER, THE COMBINATION INCLUDING A TESTING VESSEL, A BALANCE BEAM, AN HYDROMETER SUSPENSION FROM ONE END OF THE BALANCE BEAM AND HAVING LOCATION IN THE TESTING VESSEL; INDUCTANCE COILS ASSOCIATED WITH THE OTHER END OF THE BALANCE BEAM IN A MANNER WHEREBY THE IMPEDANCE OF THE COILS IF BALANCED ONLY WHEN THE BEAM IS DISPOSED IN A HORIZONTAL NEUTRAL POSITION, MEANS CONTINUOUSLY DELIVERING A QUANTITY OF LIQUID SUSPENSION TO THE TESTING VESSEL TO SUBMERGE THE HYDROMETER THEREIN AND EFFECT MOVEMENT OF THE BALANCE BEAM AS THE DENSITY OF THE LIQUID SUSPENSION MAY VARY, AND OTHER MEANS RESPONSIVE TO THE BALANCED AND UNBALANCED CONDITIONS OF SAID INDUCTANCE COILS FOR DIVERTING THE LIQUID SUSPENSION DELIVERED THERETO TO A BATH CIRCUIT WHEN THE SAME HAS THE CORRECT DENSITY OR A HIGHER DENSITY, AND FOR DIVERTING THE LIQUID SUSPENSION TO A RETURN CIRCUIT FOR THICKENING WHEN THE DENSITY OF THE SAME IS BELOW THE CORRECT DENSITY. 